NBS best estimate from pooled data of isotopic composition of uranium standards (atom %)

SRM No.	U234	U235	U236	U238	235/238
U005	0.0022	0.4896	0.0047	99.5035	0.004920
U010	.0054	1.0038	.0068	98.9840	.010141
U015	.0085	1.5322	.0164	98.4429	.015564
U020	.0125	2.0383	.0165	97.9327	.020813
U030	.0190	3.0459	.0204	96.9147	.031429
U050	.0279	5.0089	.0480	94.9152	.05277
NBS certified values (atom %)
U100	0.0676	10.190	0.0379	89.704	0.11360
U150	.0993	15.307	.0660	84.528	.18109
U200	.1246	20.013	.2116	79.651	.25126
U350	.2498	35.190	.1673	64.393	.5465
U500	.5181	49.696	.0755	49.711	.9997
U750	.5923	75.357	.2499	23.801	3.166
U800	.6563	80.279	.2445	18.820	4.266
U850	.6437	85.137	.3704	13.848	6.148
U900	.7777	90.196	.3327	8.693	10.375
U930	1.0812	93.336	.2027	5.380	17.349